There is no electrical energy in nature that can be directly used. Although natural phenomena, such as thunder and lightning, generate some electrical energy, it is difficult to be used as a power source. Therefore, the electrical energy used by humans is converted from mechanical energy, thermal energy, chemical energy, solar energy and the like. In many cases, such electrical energy converted from the mechanical energy, the thermal energy, the chemical energy and the solar energy is inconsistent with use requirements, thus another conversion is required to convert one form of electrical energy into another form of electrical energy. Energy conversion and energy transfer devices are prevalent in people's daily lives and are widely used.
The electrical energy can be divided into two categories: Alternating Current (AC) and Directing Current (DC), and the energy conversion devices can be divided into four types: AC-AC conversion, AC-DC conversion, DC-AC conversion and DC-DC conversion. The AC-DC conversion and the DC-AC conversion are relatively easy to be understood. For the AC-AC conversion, objects that can be converted include frequency, phase, voltage and current. For the DC-DC conversion, objects that can be converted include voltage and current. Methods for monitoring and assessing performance of an electrical device can be roughly divided into two categories:
One is to monitor whether there is energy output in the device, and based on this, to implement rough management. Advantages of this method are simple principle and convenient monitoring, and its drawback is inability to implement meticulous management of the device.
The other is to monitor information, such as on/off state of an input circuit and output circuit, magnitude of voltage, magnitude of current, temperature level, etc., in real time inside the device by designing an intelligent monitoring unit within the device, and send the related information to the next upper-level intelligent monitoring device to perform meticulous management. The drawback is that the structure of the intelligent monitoring unit is complicated, and the reliability of the intelligent monitoring unit itself is required be solved since the intelligent monitoring unit and the device operate together in relatively harsh environment, such as high temperature, high humidity, strong interference, electrostatic, and the like.
Either the first method or the second method can not give accurate performance assessment for a sub-health state of the monitored device, such as degraded performance and increased loss caused by harsh use environment, material aging and other reasons.